import numpy as np
arr = np.array([[1,2,3],[4,5,6],[7,8,9],[10,11,12]])
# print('4x3的整数数组：\n',arr)
# print('数组的ndim属性：',arr.ndim)
# print('数组的shape属性：',arr.shape )
# print('数组的size属性：',arr.size)
# print('数组的dtype属性：',arr.dtype)
print(arr[2])
print(arr[1:5])
print(arr[:8:2])
print(arr[::3])

